The present invention relates to pastry production line equipment. More specifically, the present invention relates to a dough sheet former for forming a sheet of dough.
Dough sheet formers are widely used in the baking industry. Dough sheet formers typically take some quantity of dough, in the form of a ball or other mass, and form a sheet from the mass of dough. Conventional dough sheet formers involve a number of rollers. The dough mass is typically conveyed through a plurality of sets of rollers, or back and forth through a single set of rollers, to flatten the dough and form the dough into a sheet.
The sheet, once formed, is commonly conveyed to other dough processing equipment for further processing. Such processing can include further reduction of the dough, as well as cutting or shaping the dough.
This conventional form of dough sheet formation has significant drawbacks. Moving a mass of dough through rollers to form a sheet produces a shear stress in the dough. Shear stress contributes to several undesirable qualities in the dough. For example, the shear stress can substantially impair or destroy rising in the dough. Shear stress can also significantly reduce shelf life and adversely affect fat absorption properties of the dough.
Thus, there have been attempts to produce dough sheet formers which create sheets of dough, from another mass of dough, without the use of rollers in order to overcome the problems created by the shear stress developed in the dough. One such attempt is set out in Japanese Patent No. 3-266929(8) assigned to Oshikiri of Tokyo, Japan, which was applied for in the Japanese Patent Office on Mar. 17, 1990, which issued on Jul. 13, 1993, and which is entitled "Device for Delivering Belt-Shaped Dough" (hereinafter referred to as "the Oshikiri reference"). The entire specification of the Oshikiri reference is hereby incorporated by reference.
The dough sheet former set out in the Oshikiri reference includes a hopper for receiving the dough. Dough moves down through the hopper into a chamber through which a rectangular shaped piston reciprocates. The chamber communicates with the hopper through an opening which is opened and closed, in synchronisity with reciprocation of the piston, by a shutter. The shutter opens as the piston withdraws to its non-extended position. This allows the piston to create a vacuum in the chamber and draw dough from the hopper into the chamber. The shutter then closes, sealing off communication between the chamber and the hopper. The piston then begins its reciprocating stroke, forcing dough through an output end of the chamber. The output end of the chamber is equipped with a nozzle that enlarges as dough is being pushed through it by the piston, and narrows as the piston withdraws. This inhibits the dough already extruded from being drawn back into the chamber by the vacuum created when the piston withdraws into its non-extended position.
However, the dough sheet former set out in the Oshikiri reference is limited in its effectiveness for a number of reasons. First, in the Oshikiri reference, the piston, the shutter and the nozzle are all driven by a single motor. The motor has a cam assembly which fixedly determines the relative timing of movement of the shutter, the piston and the nozzle with respect to one another. Thus, the length of travel of the shutter and the piston is also fixed by the physical characteristics of the cam assembly.
The fixed nature of this timing relationship poses significant practical problems, as not all dough can be processed in the same manner. In fact, it is desirable to vary processing of even a single batch of dough during a single processing period. For example, it is widely recognized that it is desirable to achieve a constant weight extruded per unit of time, or a constant volume at the output of the dough sheet former. Thus, dough which has different densities must be processed at different rates.
In addition, when the hopper is full of dough, more dough will be forced into the chamber, and hence be forced through the nozzle by each stroke of the piston than when there is very little dough in the hopper. Thus, dough processed early in the cycle is more dense than the dough processed later in the cycle. Also, many doughs include yeast. Yeast creates gas in the dough which changes the density of the dough. If the temperature of the dough is relatively high as it is introduced into the hopper, the density (and consequently, the specific gravity) of the dough can change significantly during a single processing cycle due to the action of the enzymes contained in the yeast.